Field of the Invention
The present invention relates to a method for generating a panoramic image.
Description of Related Art
In the context of the present invention a panoramic image is understood to mean an image which can be acquired by means of a plurality of optical cameras, the individual images of which arc combined to form the panoramic image and wherein the field of view displayed by the panoramic image is greater than the fields of vision associated with the optical cameras with which the individual images have been acquired. Field of view is understood here to mean that part of the surrounding area seen from a determined position and orientation which can be viewed by an optical camera or can be displayed by the panoramic image.
Panoramic images can for instance provide information about infrastructure which can be used by governments, estate agents, utility companies, banks, insurance companies and others for the purpose of evaluating local situations, for instance the location of property, the state of infrastructural objects and local traffic situations.
In view of the above stated application an important requirement for panoramic images is that the dimensions of the elements in the image, such as the height or width of a building or road, are sufficiently accurate.
There is also a constant desire to increase the resolution of the panoramic images. Because the resolution of the optical cameras is not sufficient, a plurality of optical cameras have to be used.
A further requirement is that the individual images used to generate the panoramic image can be acquired by means of a system mounted on top of or on a moving vehicle, and that the optical cameras can record the images while the vehicle is in motion. If this were not the case, it would be more difficult to collect a sufficient number of images for a large area such as a region, local area or country.
A known problem when combining multiple images is that these images have generally not been acquired from the same position and with the same optical camera. Parallax errors will hereby occur. A number of techniques are known for preventing these errors.
In a first technique use is made of a rotatably mounted optical camera. By not displacing but only rotating the camera, multiple images can be acquired from more or less the same position. A drawback of this technique is that it is not suitable for acquiring images from a moving vehicle.
A further known technique is known from US 2002/0089765 A1 and relates to placing of optical cameras and mirrors in a frame such that light incident on a mirror is reflected to an optical camera, this in a way such that the virtual entrance pupil associated with this optical camera is the same as in the other cameras in the frame. This achieves that all cameras view images virtually from the same position, despite the fact that the cameras all have a different orientation. A drawback of this technique is that obtaining an identical virtual entrance pupil for all cameras imposes requirements in respect of placing of the cameras, whereby this approach is less suitable for increasing the number of cameras, particularly because the desired placing is sometimes impossible because of the physical dimensions of the cameras.
Another technique is known from EP 1 903 534 A1 and relates to two optical cameras which arc placed one behind the other on a longitudinal axis of a vehicle on the roof of this vehicle. Because the vehicle moves it is possible to achieve by means of a suitable control of the cameras for recording an image that, at the time the image is being recorded, each camera is located at the same position relative to the surrounding area. A drawback of the technique is that it is limited to cameras placed one behind the other in the longitudinal direction of the vehicle. The increasing in the number of cameras can hereby be described as limited. Another drawback is that parallax errors can still occur when bends are negotiated.